Starting from rest , a body slides down at `45^(@)` inclined plane in twice the time it takes to slide down the same distance in the absence of friction. The coefficient of friction between the body and the inclined plane is

Options

A. 0.33
B. 0.75
C. 0.25
D. 0.8

Explanation

On smooth surface
`a_(1)=gsin theta`
On rough surface
`a_(2)=gsin theta - mug cos theta`
`s=(1)/(2)at^(2)rArr t prop (1)/sqrt(a)`
`(t)/(2t)=sqrt((gsin theta-mug cos theta)/(gsin theta))`
`(1)/(4)=1-mucot theta`
`mu=(3)/(4)=.75`